First Tunnel Discovery
On November 15, 1974, a South Korean Army reconnaissance patrol discovered for the first time a North Korean invasion tunnel in the Demilitarized Zone northeast of Goranpo in Yeoncheon County, Gyeonggi Province. Five days later, during an investigation of the tunnel, an explosive device installed by
Start Nov 15, 1974Last edited Oct 15, 2026, 2:51 PM
Overview
The First Tunnel is a North Korean infiltration tunnel discovered on November 15, 1974, within the Demilitarized Zone (DMZ) northeast of Goranpo in Yeoncheon County, Gyeonggi Province. It was the first invasion tunnel confirmed, and it revealed that North Korea had prepared underground passages in addition to ground infiltration. It is located about 65 km from Seoul.
Discovery
According to the English Wikipedia, a South Korean Army reconnaissance patrol noticed steam rising from the ground and dug at that spot, finding the tunnel. The Korean Wikipedia records the discovering unit as a reconnaissance team of the 25th Infantry Division. While the patrol was digging, North Korean guard posts opened automatic weapons fire, and South Korean forces returned fire while investigating the site. The Korean Wikipedia gives the discovery date as November 5, but the English edition and most sources give November 15.
Structure
The tunnel was about 90 cm wide and 1.2 m high, built at a shallow depth of 2.5 to 4.5 m underground by fitting together concrete panels. It extended more than 1 km south across the Military Demarcation Line. Inside were electrical wiring and lighting, storage space for weapons, and sleeping quarters, and a narrow-gauge track and carts for hauling soil were also laid. The Korean Wikipedia gives the total length as about 3.5 km and states that more than one regiment of armed troops and heavy weapons could pass through it in one hour.
Explosion Accident
Five days later, on November 20, during an investigation of the tunnel by a United Nations Command investigation team, an explosive device that North Korea had installed detonated. The explosion killed U.S. Navy Lieutenant Colonel Robert M. Ballinger and South Korean Marine Corps Major Kim Hak-cheol, and injured five U.S. soldiers and one South Korean soldier. The United Nations Command condemned the tunnel and the explosion as violations of the Armistice Agreement at the Military Armistice Commission.
Significance
With the discovery of the First Tunnel, South Korean forces began tunnel surveys along the entire length of the DMZ. The following year, the Second Tunnel was confirmed in Cheorwon. Because the First Tunnel lies inside the DMZ, unlike other tunnels it has not been opened to the public as a general tourist site.
References
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This page is based on “제1땅굴 발견” from OpenHistory, CC BY-SA 4.0 used under the license. The original authors are listed in its page history.
Last edited Oct 15, 2026, 2:51 PM · r76386 · Text is available under CC BY-SA 4.0.